The present invention relates generally to a sealless pump for fluids and is particularly directed to a magnetic drive pump which is a sealless pump in which an impeller is located in a first compartment and a drive means is located in a second compartment which is completely closed from the first compartment by a containment can. A first magnet ring is fixed to the impeller. A second magnet ring is fixed to the drive means and is in driving alignment with the first magnet ring. The second magnet ring is rotated by the drive means which, in turn, causes the first magnet ring to rotate along with the impeller which is attached to the first magnet ring. The impeller is fixed to a shaft which is journaled to the pump housing. The impeller extends in cantilever fashion from one end of the shaft. The impeller has an inlet orifice which faces the inlet opening of the pump housing and an outlet orifice which faces the outlet of the pump housing. A hardened inner wear ring is fixed to the impeller between the inlet and outlet orifices. There is a relatively small gap between the inner and outer wear rings which prevents contact between the rings during running of the pump and limits the back flow of liquid through the gap to the inlet opening.
One of the major problems which has to be dealt with in the sealless magnetic coupling pumps described above, is the generation of heat in the containment can by eddy currents from the magnetic coupling. In order to deal with the problem of generated heat within the pump, the pump housing is provided with passageways for conveying some of the fluid which emerges from the outlet orifice of the impeller to the compartment which contains the inner magnet ring for the purpose of cooling the containment can and lubricating the journal bearings. The fluid passes back to the impeller through the journal bearings of the shaft and also cools the bearings and the shaft. If the temperature of the magnetic drive components is not kept under control, the journal bearings become too hot and lock, resulting in damage to one or more of the drive components. The flow of fluid through the journal bearings must be sufficient to maintain the temperature of the bearings and shaft below a critical temperature. At the same time, this back flow reduces the pumping efficiency of the pump. These and other difficulties experienced with the prior art sealless pumps have been obviated by the present invention.
It is, therefore, a principle object of the invention to provide a magnetic drive pump which does not require journal bearings in the containment can area, thereby reducing generated heat within the coupling area and eliminating the problem of bearing lock from heat generated by the magnetic coupling.
Another object of this invention is the provision of a magnetic drive pump which permits a reduced back flow of liquid from the magnetic coupling region of the pump to the inlet opening of the pump, thereby resulting in increased pumping efficiency.
A further object of the present invention is the provision of a magnetic drive pump in which the wear rings, which are normally associated with the impeller, function as both back flow limitating devices and journal bearings for the impeller and components which are directly connected to the impeller, including the driven magnet ring and are the only bearings needed for these components.
It is another object of the present invention to provide a magnetic drive pump in which journal bearings of the impeller are isolated from the magnetic coupling components and are thereby unaffected by the heat which is generated by the magnetic coupling components.
A still further object of the invention is the provision of a magnetic drive pump in which journal bearings for the impeller are located near the inlet opening of the pump housing and are located upstream or at the relatively cool portion of the back flow of pumped fluid which is used for cooling the magnetic coupling means so that the general bearings are unaffected by heat which is generated from the magnetic drive coupling.
It is a further object of the invention to provide a magnetic drive pump which is much simpler and compact in construction than conventional pumps of this type and which is capable of a long life of useful service with a minimum of maintenance.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.